Structural panels having sheetmetal-covered cores of styrofoam, or other suitable insulating material, are in widespread use. A multitude of different designs have been created and patented; typical prior art designs are shown in U.S. Pat. No. 4,769,963 to Meyerson, U.S. Pat. No. 4,065,902 to Lindal, U.S. Pat. No. 3,228,162 to Gregoiere, U.S. Pat. No. 3,479,784 to Massagli, U.S. Pat. No. 4,438,614 to Raith, et al., U.S. Pat. No. 3,331,173 to Elsner, U.S. Pat. No. 2,284,229 to Palmer, U.S. Pat. No. 4,373,312 to Kim, U.S. Pat. No. 3,367,076 to O,Brien, U.S. Pat. No. 3,742,672 to Schaeufele, and U.S. Pat. No. 4,186,539 to Harmon, et al.
Foreign patents of interest include British patent 1,066,701, British patent 2 168 732A, and French patent no. 2 444 762.
These earlier designs have a common drawback: they leak when used as roofing panels. The complex joint constructions shown in the above-mentioned patents and in many other non-patented designs were intended to provide tight seals against water penetration, but as every owner of a structure having a roof made of metal-faced panels knows, water leaks through the joints of even the most expensive panels.
Leakage occurs, of course, at the seams between contiguous panels. The art teaches that proper application of a good caulking compound at each seam will adequately protect against moisture intrusion; the art also teaches that the panels should not be walked upon after the caulking procedure has been completed because the panels flex at the seams when walked upon and the caulking compound cracks in response to such flexing, especially if the compound is brittle from prolonged solar exposure. Cracked compound, obviously, is pervious to water.
When the teachings and suggestions of the prior art are viewed as a whole in compliance with the requirements of law, those of ordinary skill in this art are impelled to develop better caulking compounds and are repelled from walking on roofs having seams sealed with brittle caulking compound.